Rivalität oder Zufall: was verursacht das Aussterben von marinen Top-Prädatoren?

• Antragstellerin: Dr. Stefanie Klug
• Fachliche Zuordnung: Paläontologie
• Förderung: Förderung von 2013 bis 2015
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 234117688

Two key driving forces of evolution cause the amazing diversity on Earth: speciation and extinction. The main organism-controlled underlying process of such reorganisations of ecosystems is 'competitive replacement'. However, so far, any attempt to track competitive replacements in the fossil record has failed leading to the postulation that such a process might have played only a tangential role in evolution. But this assumption is in stark contrast to the fact that competitive replacement is repeatedly observed in recent habitats.Previous studies have shown that searching for rival patterns among fossils to test the theory of competitive replacement is challenging. First, any non-competitive inducing factors for extinction have to be excluded. Second, and even more crucial, is the appropriate choice of competing groups, which should be closely related, comparable in their morphology, and that should have similar ecological, environmental and feeding preferences.Two cartilaginous fish clades serve as an excellent case study to investigate the competitive replacement hypothesis and to overcome the problems and shortcomings of previous studies: the Neoselachii (modern sharks, skates and rays) and the extinct Hybodontoidea. Both groups not only meet all the above-mentioned requirements but also are the most successful shark groups ever lived, as top predators in our oceans.In this study the hypothesis will be tested that neoselachians superseded hybodonts in the marine realm, expelled them partially into freshwater habitats and finally drove them to extinction in both habitats at the Cretaceous/Paleogene boundary. As such, this would be the first evidence for competitive replacement in the fossil record. The examined period spans 230 million years from the Early Permian, the origin of neoselachians, to the disappearance of hybodonts and thus covers the outset and progress of competition and superseding. This long cycle provides invaluable information on the response of marine top predators to natural experiments in driving forces of survival and extinction. This will enable us to understand 1) the reasons and course of top predator extinction and 2) patterns of competitive replacement.By applying the most comprehensive approach so far, the major objectives of this project will be initially to construct the first global diversity curves for both groups corrected for a wide range of sampling biases. In a second step, the biotic and abiotic influences on their diversity, ecology and distribution apart from rivalry will be investigated. These patterns will then be used to trace processes of competition in order to test the hypothesis of competitive replacement in marine top predators.

• DFG-Verfahren: Forschungsstipendien
• Internationaler Bezug: Großbritannien
• Gastgeberinnen / Gastgeber: Professor Mike Benton; Dr. Daniela Natalie Schmidt